Conventionally, a valve control apparatus has a valve which opens/closes an intake passage communicating with a combustion chamber of an internal combustion engine, a shaft supporting the valve, and an actuator driving the valve in order to control an intake air flow rate. The actuator has an end-gear receiving a driving force from an electric motor (driving source). The end-gear is connected to the shaft, so that the valve and the actuator are connected to each other. Refer to JP-2004-124933A (GB-2393218A) and JP-2009-013934A (US-2009/0007875A1).
FIG. 6 shows a valve control apparatus 100 shown in JP-2004-124933A. An actuator 101 is provided with an end-gear 103 which is made of resin material and receives a driving force from an electric motor (driving source). A shaft 104 made of metallic material is press-inserted into a hole 106 of the end-gear 103, whereby the shaft 104 is connected with the end-gear 103. A rotation of the end-gear 103 is transmitted to the valve 107 through the shaft 104.
A housing 109 has a stopper (not shown) to which a stopper-portion (not shown) of the end-gear 103 confronts so that an operation range of the valve 107 is regulated. That is, the stopper regulates an angular operation range of the end-gear 103 so that the operation range of the valve 107 is restricted. Further, the valve control apparatus 100 is provided with a sensor (not shown) which detects a rotational angle of the end-gear 103, so that a position of the valve 107 is detected.
In this valve control apparatus 100, since the valve 107 is connected to the actuator 101 by press-inserting the shaft 104 into the end-gear 103, its manufacturing cost is relatively low.
However, in this valve control apparatus 100, if a press-inserting portion between the shaft 104 and the end-gear 103 is damaged, the sensor detecting the rotational angle of the end-gear 103 can not detect this malfunction. That is, a malfunction in a driving-force-transmitting path can not be detected.
If the press-inserting portion is broken, it is likely that the rotation of the end-gear 103 is restricted by the stopper and only the shaft 104 may spin free. In such a case, even though the end-gear 103 is restricted by the stopper, the valve 107 rotates over a restricted range. Since the sensor detects only the rotational angle of the end-gear 103, it can not be detected that the valve 107 rotates over the normal range.
In order to detect the above malfunction, it is conceivable that another sensor directly detecting a rotational angle of the shaft 104 is necessary. However, another sensor increases the manufacturing cost.
FIG. 7 shows a valve control apparatus 200 shown in JP-2009-013934A. A sensor 201 directly detects a rotational angle of a shaft 202 so that an opening degree of the valve 203 is detected. If the shaft 202 rotates over a normal rotational range of the valve 203 due to a breakage in a connection portion between a shaft 202 and an end-gear 204, the sensor 201 outputs a detection value which indicates that the rotational angle of the shaft 202 is abnormal. Thus, it can be detected that the valve 203 has a malfunction.
However, in this valve control apparatus 200, a configuration of connecting portion between the valve 203 and the actuator 205 becomes complicated. Further, a gear-holding member 206 for connecting the end-gear 204 to the shaft 202 and a sensor-holding member 208 for holding a magnet 207 on the shaft 202 are necessary, which increase the number of parts and increase the manufacturing cost. Thus, even in the valve control apparatus 200, a malfunction in a connecting portion between the shaft 202 and the end-gear 204 is not detected with low cost.
It is well known that an electric driving apparatus drives a valve, which corresponds to a driven member, by use of a driving force of an electric motor. The electric driving apparatus is applied to a valve control apparatus for an internal combustion engine, which adjusts an intake air quantity or an exhaust gas quantity.
The electric driving apparatus is provided with a mechanism which holds a mechanical position of the driven member. For example, in a case that the electric driving apparatus is applied to a tumble-control-valve (TCV) apparatus, a reduction-gears mechanism is provided with a stopper so that the driven member is mechanically held at a full-open position or a full-close position.
In such an electric driving apparatus, when the driven member is mechanically held, the electric current supplied to the electric motor is stepwise increased. For example, when the TCV-apparatus rotates a tumble-control valve toward the full-close position, the electric current supplied to the electric motor varies as shown in FIG. 17. That is, when the electric motor is energized, the electric current is temporarily rapidly increased due to an inrush current, and then the electric current is decreased. When the unheld driven member is mechanically held, the electric current supplied to the electric motor is stepwise increased. When the driven member is not mechanically held, the condition of the driven member is referred to as an unhold condition, hereinafter. Also, when the driven member is mechanically held, the condition of the driven member is referred to as a hold condition, hereinafter.
It has been needed to correctly determines whether the condition of the driven member is normally changed from the unhold condition to the hold condition without respect to the stepwise increase in the electric current.
JP-8-19172A and JP-2005-151766A show an electric circuit configuration in which it is determined that a malfunction occurs when the electric current supplied to the electric motor exceeds a specified threshold. However, in this electric circuit, the change from the unhold condition to the hold condition is not determined as a normal change.
JP-2001-4674A shows an electric circuit configuration in which the supplied electric current is integrated so that an over-current due to a short circuit is distinguished from a normal electric current increase due to the condition change from the unhold condition to the hold condition. However, in this electric circuit, it is likely determined that no malfunction occurs even if a malfunction other than over-current occurs.